In the field of organic semiconductors, organic light-emitting diodes (OLEDs) in particular have become known to date as light-emitting components. A distinction is drawn between OLEDs formed from low molecular weight compounds and OLEDs formed from polymers. While the OLEDs formed from low molecular weight compounds, better known by the term “small molecules”, give rise to very efficient components with the aid of multilayer systems, the advantage of polymeric OLEDs lies in the simpler and less expensive manufacturing operations.
The novel component type of light-emitting electrochemical cells shares the inexpensive mode of manufacture of the polymer OLEDs. An OLEEC in the simplest case has only a single active layer comprising various ionic compounds. Only in operation of the component, i.e. only after application of a component voltage, are the negatively charged moieties of the ionic compounds aligned in the direction of the anode, while the positively charged moieties of the ionic compounds are aligned in the direction of the cathode. By means of this ion migration, what is called a p-i-n structure thus forms in the operation of the component, like that which has to be implemented, for example, in the OLED by a multilayer deposition. In this context, p stands for p-conductive, i for intrinsic and n for n-conductive. Predominantly the ions of the so-called matrix material are responsible for the formation of this p-i-n structure. The matrix materials used are preferably ionic liquids. These ions make more of a contribution to the buildup of the internal electrical field in operation than they do to the direct transport of charge.
As well as the matrix material, there is a second ionic component in the active layer. This is usually referred to as the emitter, but, as well as the task of emitting light, equally fulfills the task of the charge transport component. For this purpose, the so-called emitter is present in the active layer in very high concentration, usually well above 50%. The accomplishment of these two tasks, light emission and current transport, places high demands on the emitter material. The latter is very highly stressed in operation, which distinctly shortens its lifetime. Moreover, especially at high luminances, there is triplet-triplet annihilation which greatly lowers the efficiency of the emitter. One reason for the triplet-triplet annihilation can be derived from the knowledge gained in the OLED sector, that it is attributable to the high emitter concentration. However, this cannot be reduced arbitrarily by the present concept.